As an HR consultant with a major global HR firm, I really enjoyed this article about selecting an HR consulting partner. I would also say the below rules also apply to selecting a good vendor. Not all vendor relationships are like this, but a good HRO relationship will be.
All following text from HR.com
Most HR people are called upon at one time or another to evaluate consulting options and even recommend who ought to be hired. Unfortunately, the process is usually worthless, since all the wrong questions are asked and all the wrong factors applied.
Here’s what you should know about any consultant or consulting firm worth working with you:
1. They are evaluating you just as you are evaluating them. They are not looking for a “sale,” but rather for a partnership. Good consultants will be judging whether or not they want to work with your firm.
2. They will insist on meeting the buyer. Tuck your ego away. It’s an ethical necessity to meet with the person who is actually authorizing the investment and who will be the true partner. If a consultant doesn’t demand this, then he or she isn’t acting in your best interests.
3. They will have references at the right time. No one is going to provide you with valuable references (who shouldn’t be called often) at preliminary meetings and in early discussions. But impressive references should be available at the time that a proposal is requested. (In the meantime, you can evaluate credibility based on the consultant’s discourse, collateral materials, web site, suggestions, demeanor, etc.)
4. They will agree to provide a written proposal with options, so that your company can evaluate ROI alternatives. That proposal should be based on business outcomes (e.g., increased sales, decreased attrition, better teamwork) and NOT “deliverables” (e.g., training sessions, reports, manuals, etc.).
5. They will not suggest nor convey an off-the-shelf resolution to your issues. (Training companies provide pre-packaged “solutions” for a set price; consultants do not. That’s one way to tell the difference, no matter what the business card claims.)
6. They will “push back,” and not merely respond to your requests. Good consultants ask “Why?” when you tell them you want something, and attempt to determine what you really need, which may be different from what you think you want. That’s why you’re assessing outside help.
7. Finally, they will transfer skills to you. You should be enriched after using consultants, not just in problems solved or challenges met, but also in the continuing ability to apply what you’ve learned.
If you find, ironically, that you can intimidate and easily influence the consultant, then you’ve got the wrong person. You really need someone who will assertively tell you the truth, not what you want to hear.